Chemical Process Research Lab.

AbstractAbstract

Acetone-methanol system forms an azeotrope at 77.6% by mole of acetone inacetone-methanol mixture under atmospheric pressure Acetone can be purifiedacetone methanol mixture under atmospheric pressure. Acetone can be purifiedfrom water by pressure swing distillation process since the azeotropic compositionis very sensitive to the system pressure. Pressure swing distillation process is moreenvironmental-friendly than azeotropic or extractive distillation process becauseenvironmental friendly than azeotropic or extractive distillation process becauseazeotropic distillation process uses an entrainer and extractive distillation processutilizes a solvent.

In this study, modeling and comparison works have been performed for low-high columns and high-low columns configurations. Optimal operating conditionsthat minimize the total reboiler heat duty were determined by using feed stagethat minimize the total reboiler heat duty were determined by using feed stagelocations and reflux ratios as manipulated variables for each distillation column.Overhead vapor stream of high pressure distillation column was used as a reboilerheating source for the low pressure column to reduce high temperature and lowheating source for the low pressure column to reduce high temperature and lowtemperature utility consumptions.

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ContentsContents

A. Introduction and Basic PrinciplesA. Introduction and Basic Principlespp•• A.1 Pressure Swing DistillationA.1 Pressure Swing Distillation•• A.2 AcetoneA.2 Acetone--Methanol SystemMethanol System•• A.3 Thermodynamic TheoryA.3 Thermodynamic Theory

B. AcetoneB. Acetone--Methanol Separation using Pressure Swing DistillationMethanol Separation using Pressure Swing Distillation•• B.1 LowB.1 Low--High Pressure Column ConfigurationHigh Pressure Column Configuration•• B.2 HighB.2 High--Low Pressure Column ConfigurationLow Pressure Column Configuration

C. AcetoneC. Acetone--Methanol System SteadyMethanol System Steady--State DesignState Design•• C.1 LowC.1 Low--High Configuration Specification Summary High Configuration Specification Summary •• C.2 HighC.2 High--Low Configuration Specification Summary Low Configuration Specification Summary

D. Summary of the ResultsD. Summary of the Results•• D.1 Stream SummaryD.1 Stream Summary•• D.2 Optimization ResultsD.2 Optimization Results•• D.3 Comparison of the ResultsD.3 Comparison of the Results

E. ConclusionE. Conclusion

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A. Introduction and Basic PrinciplesA. Introduction and Basic Principles

If a binary changes composition over a moderate range of pressure, consideration should be given to using two ordinary distillation columns operating in series t diff t *at different pressures.*

pressurepressure--swing swing distillation.distillation.

Azeotrope ~ mixture of two or more liquids wherein its components cannot be altered by simple distillation because they share a y p ycommon boiling point and vaporization point.

Methods to separate an Azeotropic Mixture: E t ti Di till ti Extractive Distillation

Azeotropic Distillation Vacuum Distillation Pressure-Swing Distillation

Pressure swing distillation process is more environmental-friendly than azeotropic or extractive Pressure Swing Distillationdistillation process because azeotropic distillation process uses an entrainer and extractive distillation process utilizes a solvent.

Reference:*Seader J D Henley E J & Roper D K Separation process principles: chemical and biochemical operations 3rd ed John Wiley & Sons Inc United

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*Seader, J. D., Henley, E. J. & Roper, D. K. Separation process principles: chemical and biochemical operations, 3rd ed., John Wiley & Sons, Inc., United State of America, 2011. pp. 429-442

A.1 Pressure Swing DistillationA.1 Pressure Swing Distillation Pressure-swing distillation is a

method for separating a pressure sensitive azeotropepressure-sensitive azeotrope that utilizes two columnsoperated in sequence at two different pressures. p

simple change in press re can• simple change in pressure can alter relative volatility of the mixture

• can result to a significant change in the azeotropic composition or

Equilibrium relationshipEquilibrium relationship Relative VolatilityRelative Volatility

p penlarging the relative volatility of the components with very close boiling points

• allows the recovery of feed mixture

Reference:Figure A 1: http://users atw hu/distillation/processes us html

allows the recovery of feed mixture without adding a separating agent.

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Figure A.1: http://users.atw.hu/distillation/processes_us.htmlFigure A.2: http://en.wikipedia.org/wiki/Relative_volatility

A.2 A.2 AcetoneAcetone--Methanol Methanol SystemSystem

Acetone and methanol are widely used as solvents and

reagents in the

The acetone-methanol mixture forming a minimum

azeotrope is a frequent

This mixture cannot be separated into pure

components by con entional rectification

Acetone and methanol

reagents in the pharmaceutical and fine

industries.

azeotrope is a frequent waste in the pharmaceutical

industry. conventional rectification, but a special distillation

method.

Acetone and methanol have very similar normal boiling points (329.2 and 337.5 K)

e e

Txy Plot for Acetone & Methanol Txy Plot for Acetone & Methanol

Forms a homogeneous minimum-boiling azeotrope at 1 atm with a composition 77.6 mol%

77.6 mol% acetone 37.5 mol% acetone

Tem

pera

ture

Tem

pera

ture

pacetone at 328 K.

At 10 atm the azeotropic composition is 37.5 Composition, Mole fraction of Acetone Composition, Mole fraction of Acetonepmol% acetone at 408 K Reference:

Simsci PRO/II 9.1, Invensys System Inc., 1994-2011 Blue – T-x Plot or Bubble pointGreen – T-y Plot or Dew point

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A.2 A.2 AcetoneAcetone--Methanol Methanol SystemSystem

Vapor-Liquid EquilibriumAcetone + MethanolAcetone + Methanol

337.6

337.2

336.8

336.4

336

335.6

Vapor-Liquid EquilibriumAcetone + Methanol

1

0.9T [K

]

335.2

334.8

334.4

334

333.6

333.2

332 8

/mol

]

0.8

0.7

0.6

332.8

332.4

332

331.6

331.2

330.8

330.4

y(A

ceto

ne) [

mol

/

0.5

0.4

0.3

azeotropic point

x,y(Acetone) [mol/mol]10.90.80.70.60.50.40.30.20.10

330

329.6

329.2

10 90 80 70 60 50 40 30 20 10

0.2

0.1

0

Experimental Data Plot from Dortmund Data Bank (DDB)

x(Acetone) [mol/mol]10.90.80.70.60.50.40.30.20.10

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A.3 A.3 Thermodynamic TheoryThermodynamic TheoryLiquid Activity Method

Universal Quasi chemical (UNIQUAC)Universal Quasi-chemical (UNIQUAC)K-values: UNIQUAC methodEnthalpies, entropies, densities, vapor fugacities: Ideal method

Combinatorial part Residual partg

combinatorial part

• depends only on the sizes and shapes of the individual molecules

residual part

• accounts for the energy interactions, has two adjustable binary parameters.j y p

Reference:Simsci PRO/II 9.1,

Invensys System Inc

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Invensys System Inc., 1994-2011

M d li f th D t i i thModeling of the Pressure Swing

Distillation Process using PRO/II

Determining the Optimum Feed Stage Location

Determining the Optimum Reflux

Ratio

Determining the Minimum Total Reboiler Heat

Dutiesg

Low-High Pressure C lColumn

Configuration (1atm ~ 10atm) For Low

Pressure Column and

For Low Pressure

Column and

Comparison between the

two fi i

High-Low Pressure Column

Column and High Pressure

Column

Column and High Pressure

Columnconfigurations (LP+HP and

HP+LP)

Configuration (10atm ~ 1atm)

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AcetoneAcetone--Methanol Methanol Separation Separation using using Pressure Swing DistillationPressure Swing Distillationgg gg

Pressure DownFor ShiftingAzeotrope

OVERHEADacetone-rich methanol-rich

T01 T02FEEDPressure UpT01

Low Pressure Column

High Pressure Column

Pressure UpFor ShiftingAzeotrope

BOTTOMS

methanol-rich acetone-rich

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BOTTOMS

A. LowA. Low--High High Pressure Column ConfigurationPressure Column Configuration

10 atm1.5 atm1 atm 10 atm1.5 atm

75% Acetone 40% Acetone

N=52 N=6212 atm

High Pressure Column

Low Pressure Column

Column

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99.4% Acetone99.5% Methanol

B. B. HighHigh--Low Pressure Column ConfigurationLow Pressure Column Configuration

12 atm1 atm10 atm

75% Acetone40% Acetone

N=52N=62

1.5 atm

Low Pressure ColumnColumn

High Pressure Column

99 5% Methanol

12

99.4% Acetone 99.5% Methanol

AcetoneAcetone--Methanol Methanol System SteadySystem Steady--State State Design InputsDesign Inputs

Reference: Luyben, William L. & I-Lung Chien. Design and control of distillation systems for separating azeotropes..

FEEDComponent composition

(%mole)Acetone 50 Distillation ColumnAcetone 50Methanol 50Total Flow Rate (kg-mol/hr) 540Temperature (K) 320

Distillation ColumnSpecs Low-Pressure

ColumnHigh-Pressure

ColumnPressure (atm) 1 10

Pressure (atm) 2.5 N stage 52 62

Column pressure drop 0.1 atm 0.1 atm

Condenser condition at Bubble Temperature at Bubble Temperature

PRODUCT

Condenser condition at Bubble Temperature at Bubble Temperature

Pressure Changer

Specs Low-Pressure Column High-Pressure Column

Bottoms 99.5% methanol 99.4% acetone

Equipment Outlet Pressure

Valve (V01) 1.5Valve (V02) 1.5

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Distillate 75% acetone 40% acetone Pump (P01) 12

LowLow--HighHigh Configuration Specifications SummaryConfiguration Specifications Summary

HPC Overhead 40% AcetoneV102

Low Pressure Column

High Pressure Column

40% AcetoneV102Outlet pressure : 1.5 atm

LPC Overhead75% AcetoneV101

Outlet pressure: 1.5 atm P101Outlet pressure : 12 atm

HPCTop Pressure : 10 atm

Column pressure drop: 0.1 atmCondenser at BubbleCondenser at Bubble

Temperature

OP2Minimize Reboiler Heat Duty

Vary Feed Plate Location

LPC

OP1Minimize Reboiler Heat Duty

Vary Feed Plate Location andReflux Ratio of LPC

Vary Feed Plate Location and Reflux Ratio of HPC

LPC Bottoms99 5% M th l

Top Pressure : 1 atmColumn pressure drop : 0.1 atm

Condenser at Bubble Temperature

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HPC Bottoms99.4% Acetone

99.5% Methanol

HighHigh--LowLow Configuration Specifications SummaryConfiguration Specifications Summary

Low Pressure Column

High Pressure Column

HPC Overhead 40% Acetone

P01 and P02Outlet pressure : 12 atm

LPC Overhead75% AcetoneV201

Outlet pressure : 1.5 atm

OP2OP2Minimize Reboiler Heat Duty

Vary Feed Plate Location and Reflux Ratio of LPC

HPCTop Pressure : 10 atm

Column pressure drop : 0.1 atmCondenser at Bubble Temperature

OP1Minimize Reboiler Heat Duty

Vary Feed Plate Location and Reflux Ratio of HPC

HPC B tt LPC B tt

LPCTop Pressure : 1 atm

Column pressure drop : 0.1 atmCondenser at Bubble Temperature

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HPC Bottoms99.4% Acetone

LPC Bottoms99.5% Methanol

Condenser at Bubble Temperature

Minimization of Total Reboiler Heat DutyMinimization of Total Reboiler Heat DutyMinimization of Total Reboiler Heat DutyMinimization of Total Reboiler Heat DutyBy varying

Feed TrayFeed TrayFeed TrayFeed TrayOPT-FT

Reflux RatioReflux RatioReflux RatioReflux RatioOPT-RR

Low-High Pressure Column

C fi i

Low-High Pressure Column

C fi i

High-Low Pressure Column

C fi i

High-Low Pressure Column

C fi i

Low-High Pressure Column

C fi i

Low-High Pressure Column

C fi i

High-Low Pressure Column

C fi i

High-Low Pressure Column

C fi iConfigurationConfigurationLP-HP (1)

ConfigurationConfigurationHP-LP (2)

ConfigurationConfigurationLP-HP (1)

ConfigurationConfigurationHP-LP (2)

Low Pressure Column

Low Pressure Column

LPC

High Pressure Column

High Pressure Column

HPC

High Pressure Column

High Pressure Column

HPC

Low Pressure Column

Low Pressure Column

LPC

Low Pressure Column

Low Pressure Column

LPC

High Pressure Column

High Pressure Column

HPC

High Pressure Column

High Pressure Column

HPC

Low Pressure Column

Low Pressure Column

LPC

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Feed Tray Optimization for Feed Tray Optimization for LowLow--High High ConfigurationConfiguration

LowLow--Pressure ColumnPressure Column

HighHigh--Pressure ColumnPressure Column

Optimum MinimumFeed Stage Location Reboiler Heat Duty

Optimization ResultsOptimization Results Vary Objective Vary Objective2 ~ 50 2 ~ 60

Initial Bottoms Flow Rate

Initial Feed TrayLocation

Feed TrayLocation

ReboilerHeat Duty

Feed Tray Location

ReboilerHeat Duty Total

Low-High Pressure Configuration Feed Stage Location Reboiler Heat Duty

LPC HPC LPC HPC

38 40 11.549 6.202

Total ReboilerH t D t

17.751M*KCAL/HR

Low High Pressure ConfigurationLPC HPC LPC HPC Low Pressure High Pressure460 190 26 31 37.887 11.550 39.700 6.208 17.758460 190 37 39 37.739 11.551 39.000 6.207 17.758460 190 38 39 38.000 11.549 39.000 6.207 17.756460 190 38 40 38 000 11 549 40 000 6 202 17 751

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Heat Duty M*KCAL/HR460 190 38 40 38.000 11.549 40.000 6.202 17.751

Feed Tray Optimization for Feed Tray Optimization for HighHigh--Low Low ConfigurationConfiguration

HighHigh--Pressure ColumnPressure Column

LL P C lP C lLowLow--Pressure ColumnPressure Column

O ti i ti R ltO ti i ti R lt Vary Objective Vary Objective

Optimum MinimumFeed Stage Location Reboiler Heat Duty

Optimization ResultsOptimization Results Vary Objective Vary Objective2 ~ 60 2 ~ 50

Initial Bottoms Flow Rate

Initial Feed TrayLocation

Feed TrayLocation

ReboilerHeat Duty

Feed Tray Location

ReboilerHeat Duty Total

High-Low Pressure ConfigurationHPC LPC HPC LPC High Pressure Low Pressure Feed Stage Location Reboiler Heat Duty

HPC LPC HPC LPC

39 37 14.585 7.0884

Total ReboilerH t D t

21.673M*KCAL/HR

g190 460 31 26 41.966 14.595 37.073 7.0885 21.684190 460 42 37 39.039 14.585 37 7.0884 21.673190 460 39 37 40 14.596 37 7.0884 21.6844190 460 37 35 39.258 14.584 35 7.1153 21.699190 460 39 35 38 876 14 585 35 7 1153 21 7003

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Heat Duty M*KCAL/HR190 460 39 35 38.876 14.585 35 7.1153 21.7003190 460 36 35 38.74 14.587 35 7.1153 21.702

Feed Tray Case Study for Feed Tray Case Study for LowLow--High High ConfigurationConfiguration

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Modifying Column Specification Modifying Column Specification

Low Low Pressure Pressure ColumnColumn

High Pressure ColumnHigh Pressure Column

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Calculator InputCalculator Input

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Reflux Ratio Optimization for Reflux Ratio Optimization for LowLow--High High ConfigurationConfiguration

LowLow--Pressure ColumnPressure Column

HighHigh--Pressure ColumnPressure Column

Optimum MinimumReflux Ratio Reboiler Heat Duty

Optimization ResultsOptimization Results Vary Objective Vary Objective0.1 ~ 10 0.1 ~ 10

Initial Bottoms Flow Rate

Initial Feed TrayLocation

Reflux Ratio ReboilerHeat Duty Reflux Ratio Reboiler

Heat Duty Total

Low-High Pressure Configuration Reflux Ratio Reboiler Heat Duty

LPC HPC LPC HPC

2.2853 3.3494 11.0847 6.5622

Total ReboilerH t D t

17.6469M*KCAL/HR

Low High Pressure ConfigurationLPC HPC LPC HPC Low Pressure High Pressure460 190 26 31 2.2543 11.2527 3.2385 6.7758 18.0285460 190 37 40 2.1214 12.3097 2 6.6384 18.9481460 190 38 39 2.1308 11.0642 3 6.7575 17.8217460 190 38 40 2 2853 11 0847 3 3494 6 5622 17 6469

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Heat Duty M*KCAL/HR460 190 38 40 2.2853 11.0847 3.3494 6.5622 17.6469

Reflux Ratio Optimization for Reflux Ratio Optimization for HighHigh--Low Low ConfigurationConfiguration

HighHigh--Pressure ColumnPressure Column

LL P C lP C lLowLow--Pressure ColumnPressure Column

Optimum MinimumReflux Ratio Reboiler Heat Duty

Optimization ResultsOptimization Results Vary Objective Vary Objective0.1 ~ 10 0.1 ~ 10

RRRange

Initial Bottoms Flow Rate

Initial Feed Tray Location

Feed TrayLocation

ReboilerHeat Duty

Feed Tray Location

ReboilerHeat Duty Total

High Low Pressure Configuration Reflux Ratio Reboiler Heat Duty

HPC LPC HPC LPC

2.1772 2.6 14.2902 7.3762

Total ReboilerH t D t

21.6664M*KCAL/HR

Range y High-Low Pressure ConfigurationHPC LPC HPC LPC High Pressure Low Pressure

0.1 ~ 10 300 575 36 35 1.5696 14.0609 2 8.306 22.36691 ~ 10 575 300 37 35 1.7 14.3651 2 7.9834 22.34851 ~ 4 575 300 37 35 2.1772 14.2902 2.6 7.3762 21.6664

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Heat Duty M*KCAL/HR1 ~ 4 575 300 39 37 1.7 13.5078 2.5064 8.45512 21.9629

Reflux Ratio Case Study for Reflux Ratio Case Study for LowLow--High High ConfigurationConfiguration

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Comparison of the ResultsComparison of the Results

LPCLPC HPCHPC HPCHPC LPCLPC LPCLPC HPCHPC HPCHPC LPCLPC

No. of stages 52 62 62 52 52 62 62 52Operating Pressure (atm) 1 10 10 1 1 10 10 1

Overhead Flowrate(KMOL/HR) 458.467 188.327 574.133 304.406 461.357 190.770 589.185 319.584

Bottoms Flowrate 269 528 270 141 270 273 269 727 269 899 270 587 269 875 269 602Bottoms Flowrate(KMOL/HR) 269.528 270.141 270.273 269.727 269.899 270.587 269.875 269.602

Optimum Values 38 40 39 37 2.2853 3.3494 2.1772 2.600Reboiler Heat Duty (M*KCAL/HR) 11.549 6.202 14.585 7.0884 11.0847 6.5622 14.2902 7.3762

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Total Reboiler Heat Duty 17.751 M*KCAL/HR 21.673 M*KCAL/HR 17.6469 M*KCAL/HR 21.6664 M*KCAL/HR

ConclusionConclusion

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F. ReferencesF. References[1] Seader, J. D., Henley, E. J. & Roper, D. K. Separation process principles: chemical and biochemical

operations, 3rd ed., John Wiley & Sons, Inc., United State of America, 2011. pp. 429-442

[2] Klein, Andreas. Azeotropic Pressure Swing Distillation. Berlin University of Technology Dissertation. Berlin, 2013. pp. 6-16

[3] Luyben, William L. & I-Lung Chien. Design and control of distillation systems for separating azeotropes. [ ] y g g y p g pJohn Wiley & Sons, Inc., Hoboken, New Jersey, 2010. pp. 149-164.

[4] Hong-Mei Wei, Feng Wang, Jun-Liang Zhang, Bo Liao, Ning Zhao, Fu-kui Xiao, Wei Wei, & Yu-Han Sun. Design and control of dimethyl carbonate–methanol separation via pressure-swing distillation. Industrial g y p p g& Engineering Chemistry Research Article ASAP. American Chemical Society, 2013.

[5] Luyben, William L. Pressure-swing distillation for minimum- and maximum-boiling homogeneous azeotropes. Industrial & Engineering Chemistry Research. American Chemical Society, 2012, 51 (33), p g g y y ( )pp. 10881–10886.

[6] Kontogeorgis, Georgios M. & Folas, Georgios K. Thermodynamic Models for Industrial Applications: From Classical and Advanced Mixing Rules to Association Theories, John Wiley & Sons, Ltd., United yKingdom, 2010. pp. 109-154

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감사합니다!감사합니다!

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